1. Field of the Invention
Embodiments of the invention relate to a semiconductor integrated circuit device and a method for fabricating the semiconductor integrated circuit device. In particular, embodiments of the invention relate to a semiconductor integrated circuit device having an epitaxial layer and a method for fabricating the semiconductor integrated circuit device.
2. Description of the Related Art
Techniques for forming elevated source/drain regions have been used in forming semiconductor devices having relatively high degrees of integration. The elevated source/drain regions are formed through a selective epitaxial growth process.
In a selective epitaxial growth process, silicon is selectively grown on an active region of a semiconductor substrate by providing source gases such as dichlorosilane (DCS; SiH2Cl2) and SiH4.
When a selective epitaxial growth process is performed, an epitaxial layer can be stacked on the active region, which is defined by isolation regions. In the selective epitaxial growth process, the silicon forming the epitaxial layer grows vertically and horizontally. Thus, the silicon can grow onto the surface of an isolation region that is adjacent to the active region on which the epitaxial layer is grown.
Active regions are formed on a semiconductor substrate at regular intervals. Although a relatively large amount of space separates active regions in peripheral regions, a relatively small amount of space separates active regions in cell regions because of relatively small design rules. As a result, when an epitaxial layer extends over and is formed on isolation regions in a cell region, portions of the epitaxial layer that extend from adjacent active regions of the cell region over an isolation region separating the adjacent active regions may become connected and thereby form an active region bridge.
In addition, when the height of the epitaxial layer is adjusted such that the bridge is not formed, the semiconductor device may not benefit from the improved transistor characteristics resulting from forming elevated source/drain regions in the peripheral regions.